Advancements continue to be made in wireless communications technology. For example, wireless local area networks (WLANs) and wireless personal area networks (WPANs) networks are becoming more common in homes and businesses. Such networks may include a variety of independent wireless electronic devices or terminals, which wirelessly communicate with one another. WLANs and WPANs may operate according to a number of different available standards, including IEEE standards 802.11 (Wi-Fi), 802.15 (Bluetooth) and 802.16 (WiMax), as well as the WiMedia Alliance Ultra-Wideband (UWB) standard.
FIG. 1 is a block diagram showing a conventional wireless network 100, including multiple terminals configured to communicate with one another over exemplary WPAN 125. The wireless terminals may include any electronic devices or nodes configured to communicate with one another. For example, FIG. 1 may depict a home network in which the electronic devices include a personal computer 120, a digital television set 121, a digital camera 122 and a personal digital assistant (PDA) 123. The network 100 may also include an interface to other networks, such as modem 130, to provide connectivity of all or some of the wireless devices 120-123 to the Internet 140, for example. Of course, there are many other types of wireless networks in which electronic devices communicate with one another, including networks in manufacturing plants, medical facilities, security systems, and the like.
Wireless devices may communicate with one another using directional antennas, which extend transmission range. For example, recent wireless networks operate in very high frequency bands (e.g., 60 GHz), and thus use directional antennas to compensate for high path loss associated with high frequency bands. In both centralized and distributed wireless networks, wireless devices using directional antennas must align their respective antennas at the same time in order to communicate. In other words, the wireless devices must first find each other, which is accomplished by the wireless devices scanning (e.g., sweeping their antenna beams) around surrounding areas. However, the wireless devices may not discover one another unless there is pre-coordination among them to assure that they are sweeping their antenna beams at the same time.
Beacons are widely used to convey important control information between devices. For example, an IEEE 802.11 access point periodically sends out beacons so that the IEEE 802.11 wireless devices around the access point can associate with the access point and communicate. As stated above, if the wireless devices, including the access point, use directional antennas for beacon transmission and reception, they must know the direction of each other's antennas. This requires a protocol to coordinate the wireless devises' antenna directivity, as well as beacon transmission, reception and processing.
Otherwise, wireless devices may not be able to discover and communicate with each other even though they are in the same network 100 and in proximity to one another. Such coordination or synchronization is difficult and costly to implement. However, wireless devices not having a common time-domain reference point for coordinating antenna control and/or beacon transmission will not communicate properly as a network.
Accordingly, it would be desirable to provide a wireless device and method of wireless communications enables wireless devices to find and communicate with each other using beacons, particularly when the wireless devices are using directional antenna systems.
In one aspect of the invention, a method is provided for discovering a wireless device using a directional antenna system configured to send and receive signals in multiple antenna sectors, the wireless device being located in a first antenna sector of the multiple antenna sectors. The method includes transmitting multiple primary beacons in corresponding primary beacon time slots, the primary beacon time slots corresponding to the multiple antenna sectors and having associated multiple secondary beacon time slots. A secondary beacon is received from the wireless device in a first secondary beacon time slot associated with a first primary beacon time slot corresponding to the first antenna sector, the secondary beacon being responsive to a first primary beacon included in the first primary beacon time slot. An additional first secondary beacon time slot is added in association with the first primary beacon time slot. The additional first secondary beacon time slot enables an additional wireless device in the first antenna sector to send an additional secondary beacon in response to a subsequent first primary beacon included in the first primary beacon time slot.
The primary beacon time slots and the associated secondary beacon time slots may be contained in a superframe. The first secondary beacon time slot associated with the first primary beacon time slot may include a next consecutive time slot following the first primary beacon time slot, and the additional first secondary beacon time slot may be a next consecutive time slot following the first secondary beacon time slot. Alternatively, the first secondary beacon time slot associated with the first primary beacon time slot may follow a last primary beacon time slot of the multiple primary beacon time slots, and the additional first secondary beacon time slot may be a next consecutive time slot following the first secondary beacon time slot.
The method of discovering the wireless device may further include notifying the wireless device of receipt of the secondary beacon in the subsequent first primary beacon included in the first primary beacon time slot. Notifying the wireless device of receipt of the secondary beacon may involve including an identification of the wireless device in the subsequent first primary beacon.
The method of discovering the wireless device may further include receiving an indication of a collision associated with additional wireless devices, located in a second antenna sector, in a second secondary beacon time slot associated with a second primary beacon time slot corresponding to the second antenna sector, the collision indication being responsive to a second primary beacon included in the second primary beacon time slot. At least two additional secondary beacon time slots may be added in association with the second primary beacon time slot. The at least two additional secondary beacon time slots may enable the additional wireless devices in the second antenna sector to send associated second secondary beacons in response to a subsequent second primary beacon included in the second primary beacon time slot.
In another aspect of the invention, an apparatus is provided for communicating over a wireless network having multiple wireless devices. The apparatus includes a directional antenna system and a transceiver. The directional antenna system is configured to communicate over the wireless network in at least a first antenna sector and a second antenna sector. The transceiver is configured to send signals to the first and second antenna sectors via the directional antenna, each signal including a first transmit beacon time slot and an associated first receive beacon time slot corresponding to the first antenna sector and a second transmit beacon time slot and an associated second receive beacon time slot corresponding to the second antenna sector. The transceiver sends a first transmit beacon in the first transmit beacon time slot to the first antenna sector and a second transmit beacon in the second transmit beacon time slot to the second antenna sector. The transceiver receives a first receive beacon in the first receive beacon time slot from a first wireless device located in the first antenna sector responding to the first transmit beacon. An additional first receive beacon time slot of the signal is associated with the first transmit beacon time slot to enable an additional wireless device in the first antenna sector to send an additional first receive beacon in response to a subsequent first transmit beacon included in the first transmit beacon time slot.
The transceiver may receive a second receive beacon in the second receive beacon time slot from a second wireless device located in the second antenna sector responding to the second transmit beacon. An additional second receive beacon time slot of the signal is associated with the second transmit beacon time slot to enable an additional wireless device in the second antenna sector to send an additional second receive beacon in response to a subsequent second transmit beacon included in the second transmit beacon time slot.
The transceiver may receive an indication of a collision in the second receive beacon time slot associated with at least a second wireless device and a third wireless device located in the second antenna sector, the collision indication being responsive to the second transmit beacon. Two additional second receive beacon time slots are added in association with the second transmit beacon time slot. The two additional receive beacon time slots enable the second and third wireless devices in the second antenna sector to send associated second receive beacons.
The directional antenna system may include multiple antennas corresponding to the plurality of sectors. Alternatively, the directional antenna system may include an adaptive antenna array having multiple beams corresponding to the plurality of sectors.
The first receive beacon time slot may be paired with the first transmit beacon time slot in a dual time slot, the first receive beacon time slot including a next consecutive time slot following the first transmit beacon time slot within the dual time slot. The additional first receive beacon time slot may be a next consecutive time slot following the first receive beacon time slot within the dual time slot. The first receive beacon time slot may follow the second transmit beacon time slot. The additional first receive beacon time slot may be a next consecutive time slot following the first receive beacon time slot. The transceiver may send an announcement that a length of a beacon period will increase before the additional first receive beacon time slot of the signal is associated with the first transmit beacon time slot.
In another aspect of the invention, an apparatus is provided for communicating over a wireless network of multiple wireless devices. The apparatus includes a directional antenna system configured to communicate over multiple antenna sectors. The apparatus also includes a transceiver configured to send signals to the antenna sectors via the directional antenna, each signal including a superframe having multiple primary beacon time slots and associated secondary beacon time slots corresponding to the antenna sectors. The transceiver sends multiple primary beacons in the multiple primary beacon time slots and receives at least one secondary beacon in one of the secondary beacon time slots from a responsive wireless device located in an antenna sector associated with the received secondary beacon. The one of the secondary beacon time slots is assigned to the responsive wireless device and an additional secondary beacon time slot, associated with the antenna sector of the responsive wireless device, is added to the superframe.